The present invention relates to a motor-vehicle door latch. More particularly this invention concerns a damped actuating system for such a latch.
A motor-vehicle door latch mounted in a motor-vehicle door (which term is here also intended to cover a trunk lid or hood) is typically actuated by an element that is formed as a handle. The handle is pulled on the outside of the door to unlatch and open the door and is similarly pulled on the inside of the door to unlatch the door and allow it to be pushed open.
The handle is normally spring loaded to return to its starting position once released. In order to prevent this action from damaging the structure or creating an annoying noise, it was standard to provide an elastomeric bumper to stop the handle""s return movement somewhat more gently than just allowing the hard parts to come together. This system was replaced as described in U.S. Pat. No. 5,092,642 with an arrangement using a hydraulic damper which was coupled to the mechanism and which was effective on the return movement to slow this movement and bring the handle to a gentle rest. The damper comprises a closed housing filled with a viscous liquid and provided with a wheel having radially projecting vanes cooperating with at least one other vane fixed in the housing so that when the wheel is forcibly rotated, the liquid is forced through a small gap or orifice between the vanes.
When the latch-actuating element is set up as described in U.S. Pat. No. 5,681,068 so that it performs an unlocking/unlatching function when moved in one direction, normally outward from the door, and another function, normally locking, when pushed inward, it is possible for the released handle to overtravel and move inward. Thus if the handle is pulled all the way out and released suddenly, it will go all the way in and lock the door, which is frequently not desired.
Another system is described in U.S. Pat. No. 5,743,575 which has a hydraulic damper mounted right at the pivot for a pull-type outside door handle. Such a damper is highly effective but difficult to install. Furthermore setting it up for different damping characteristics or otherwise varying the installation is virtually impossible.
It is therefore an object of the present invention to provide an improved damped actuating system for a motor-vehicle door latch.
Another object is the provision of such an improved damped actuating system for a motor-vehicle door latch which overcomes the above-given disadvantages, that is which is of simple construction, which can be installed and modified easily, and which effectively prevents inward overtravel of the actuating element it is connected to.
The actuating system according to the invention has a handle pivoted about a handle axis on the door, an actuating part fixed on the handle and extending radially from the axis, and a damper fixed on the door adjacent the axis and having an input element. The actuating part is connected to the input element for displacement of the input element and operation of the damper on pivoting of the handle. According to the invention the input element is rotatable about a damper axis and the connection is a positive rotational coupling.
In accordance with the invention the coupling includes gear teeth on the actuating part and gear teeth on the rotary input meshing with the actuating-part gear teeth. More specifically the rotary input element is a gear wheel and the actuating part includes a sector gear in mesh with the gear wheel. Alternately the rotary input element is a wheel and the actuating part includes a wheel centered on the handle axis with a flexible transmission element reeved over the wheels and coupling them together. With either system changing of the relative diameters of the gears or wheels changes the transmission ratio and thereby allows the damping characteristic to be changed.
The door according to the invention is formed with a seat provided with means for releasably retaining the damper in the seat. This retaining means includes two elastically deformable arms defining the seat and gripping the damper. Thus mounting the damper simply entails snapping it into place. The damper can be supplied separately and easily installed in the latch, and replaced if necessary.
The damper seat can be adjustable for different transmission ratios between the actuating part and the input element. This can be done by providing a plurality of seats at different spacing, or means for moving the damper in one seat.
The damper in accordance with the invention includes a housing, a body of liquid in the housing, means defining an orifice in the housing, and at least one vane connected to the input element for forcing the liquid through the orifice on displacement of the input element. The liquid can be changed to vary the damping characteristic of the unit.
The rotary input element can include a one-way clutch by means of which it is connected to the actuating element so that the damper is only effective in one direction of movement of the handle relative to the door. Similarly a one-way valve could be provided in the damper to provide unidirectional damping action, with free movement in the opposite direction, normally the opening direction of the handle.